This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The wealth in chemistry of block copolymers allows the self assembly of block copolymer to result in abundant polymeric structures which find wide applications in nanotechnology. However, the manipulation of the chemistry of block copolymers requires careful design and tedious chemical synthesis. Herein we introduce a new assembly strategy of block copolymers in the solution state to achieve desired nanostructures in a simple manner. This paradigm involves a mixture of two or more block copolymers sharing a negatively chargeable hydrophilic carboxylic acid block but chemically incompatible hydrophobic blocks. During assembly in the aqueous mixture with positively charged amino molecules, different unique nanostructures, such as multilayer vesicles, Janus oblate nanoparticles and undulated cylindrical micelles, have been obtained due to the segregation of hydrophobic blocks within the micellar core. This process undergoes a pathway of morphological transformations determined by fast intra-micellar polymer chain reorganization as well as slow kinetics of polymeric chain exchange between individual micelles in solution. Synchrotron SAXS equipped with a beamline of high flux and high resolution has been proved by our previous experiments as a powerful global, real-time characterization method to identify the assembled structures under their original solution conditions. A complete understanding of assembly pathways enables us to develop new assembly strategies for novel polymeric nanostructures